Calculating momentum before and after a collision

In summary, the collision between a 1200 kg car and a 2000 kg truck traveling at 14 m/s and 25 m/s respectively results in a total momentum of 38,800 kg*m/s before the collision. After the collision, if the bumpers stick together, the combined mass of 3200 kg will have a speed of approximately 8.5 m/s. If the bumpers do not stick together and the car has a velocity of 5 m/s, the truck will have a speed of 7.5 m/s. The law of conservation of momentum is used to calculate the final speeds.
  • #1
sdoyle1
23
0

Homework Statement


A 1200 kg car traveling north at 14 m/s is rear-ended by a 2000 kg truck traveling at 25 m/s.
a) What is the total momentum before and after the collision?
b)If the car and truck lock bumpers and stick together, what is their speed immediately after the collision?
c) If the care and truck do not lock bumpers and the velocity of the car after the collision is 5 m/s, what is the speed of the truck after the collision?


Homework Equations





The Attempt at a Solution


I'm stuck on the concepts and my teachers hasn't gone into detail in class yet. If someone can explain the concepts then I can probably figure out the math.
 
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  • #2
Momentum is a vector quantity. In this case, you only have one component to worry about.

Formula for momentum P = mv

Also, momentum is conserved in collisions so the net initial momentum of the system is equal to the net final momentum.
 
  • #3
so would part a) just be a sum of both momentums? Or would I add the masses to get a total mass and multiply it by the total velocity (for both the truck and the car)?
 
  • #4
Momentum of a particle is defined as the product of the mass and velocity of an object.

The law you will have to use here is the "Law of Conservation of Momentum."
It says that for a system, if net external force acting on it is 0, total momentum will remain constant.

Newton's second law (in original form) is: [itex]F = - \frac{dp}{dt}[/itex]

If p is constant, F=0.
 
  • #5
sdoyle1 said:
so would part a) just be a sum of both momentums? Or would I add the masses to get a total mass and multiply it by the total velocity (for both the truck and the car)?

yes it will be sum of momenta of both truck and car
 
  • #6
Ok, I have figured out part a. How would it change if the bumpers stick together? Would the mass be the 3200 kg? How about the velocity? Would it just be the total momentum divided by the total weight?
 
  • #7
this is how collision will work:

truck is moving at higher speed than car. they collide, speed of truck dec. and that of car inc. and at some moment their speeed become equal.
then after that, car's speed inc. and that of truck dec and car starts moving faster than truck

so if they are locked together they will now have same speed and mass as sum of both car and truck
 

What is momentum?

Momentum is a measure of an object's motion, calculated by multiplying its mass by its velocity. It is a vector quantity, meaning it has both magnitude and direction.

How do you calculate momentum?

The formula for calculating momentum is: momentum = mass x velocity. The units for momentum are kg*m/s.

What happens to momentum during a collision?

During a collision, momentum is conserved, meaning that the total momentum before the collision is equal to the total momentum after the collision. This is known as the law of conservation of momentum.

How do you calculate momentum before a collision?

To calculate momentum before a collision, you need to know the mass and velocity of each object involved in the collision. Then, use the formula momentum = mass x velocity to calculate the momentum of each object separately.

How do you calculate momentum after a collision?

To calculate momentum after a collision, you can use the same formula as calculating momentum before the collision. However, you need to account for any changes in the velocities of the objects due to the collision. This can be done by using the law of conservation of momentum and setting the sum of the momentums before the collision equal to the sum of the momentums after the collision.

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